Method for adapting sensor cells of a seat mat to a mechanical prestress

ABSTRACT

A method for adjusting the sensor cells of a seat mat ( 3 ) to a mechanical stress caused by the installation of the seat mat ( 3 ) in a vehicle seat is proposed, a diagnostic tester being connected to a control unit at the seat mat, and the diagnostic tester reads out the sensor values of the seat mat and compares them to setpoint values, in order then to transmit back correcting values to the control unit, which the control unit uses in further operation for calibrating the sensor values.

BACKGROUND INFORMATION

[0001] The present invention relates to adjusting sensor cells of a seatmat to a mechanical stress, according to the species defined in the mainclaim.

[0002] From Laid-Open Document WO 97/10115 it is known that one mayadjust each sensor cell of a seat mat to a mechanical stress which isconditioned by the poor installation of the seat mat in a vehicle seat.Such a seat mat is used for determining whether there is a person on thevehicle seat, and what kind of sitting position this person has takenup, and also possibly to determine the weight of the person. These dataare then used to activate an air bag.

SUMMARY OF THE INVENTION

[0003] The method according to the present invention for adjustingsensor cells of a seat mat to a mechanical stress having the features ofthe independent claim, on the other hand, has the advantage that thestress is ascertained by the manufacturer by using a diagnostic tester,and correcting data are derived from this, with which one configures thecontrol unit, so that the measured values are corrected when the seatmat is in use. With this concept, seat mats can still be used, even withdifferent installation conditions, provided the stress lies within givenparameters, and the sensor cells are still able to measure a supportpressure caused by a sitting person.

[0004] Advantageous improvements of the method of adjusting sensor cellsof a seat mat to a mechanical stress are rendered possible by measuresand further refinements specified in the dependent claims.

[0005] It is particularly advantageous that the correcting values arestored in a memory of the control unit, so that in this memory, which isinitialized at the beginning with null values, the correcting values arepermanently available during the operating time of the control unit. Ifnecessary, even in the case of the installation of a new seat mat, thismemory is able to be overwritten with new correcting values.

[0006] It is also of advantage that, when the diagnostic tester isconnected to the control unit, first of all the diagnostic tester isinterrogated for a password, so that only one secured access to thecontrol unit and for writing on the memory of the control unit ispossible.

[0007] In addition, it is of advantage that a diagnostic tester forcarrying out the method is present which has a data transmissioninterface for connecting to the control unit, its own memory for thesetpoint values, which in this case may be a permanent memory, and aprocessor for carrying out the comparisons between the setpoint valuesand the sensor values.

[0008] It is also advantageous that a control unit for carrying out themethod according to the present invention is present, which has its owndata transmission interface for connecting to the diagnostic tester andan additional data transmission interface for connecting to the seatmat, as well as a processor, such as a microcontroller, for evaluatingthe sensor values, and a memory for accommodating the correcting values.

BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Exemplary embodiments of the present invention are illustrated inthe drawings and are explained in detail in the following description.The figures show:

[0010]FIG. 1 a block diagram of the diagnostic tester and the controlunit according to the present invention and

[0011]FIG. 2 a flowchart of the method according to the presentinvention.

DETAILED DESCRIPTION

[0012] The detection of people in the vehicle is a task gaining inimportance for restraint system. It is particularly important todetermine for which person an air bag can be used and for which it cannot. In this context, it is also possible for adaptively set air bags totrigger this air bag in the case of a collision, and a triggeringsituation resulting from this, as a function of the weight of theperson. This seeks to achieve that an optimum restraint force is exertedon the person to be protected. Besides optical and ultrasound sensors,weight sensors are also used, and, in that connection especially a seatmat having sensor elements, each sensor element being designed as apressure-sensitive resistor. These sensor elements are situated in amatrix which is interrogated cyclically by a control unit used for thisseat mat. The individual sensor elements have a lower resistance thehigher the pressure exerted on them. Using these sensor elements, it isalso possible to create seating profiles, which give out information onhow the respective person sits. By the installation of a seat mat into avehicle seat, different mechanical stresses are exerted on theindividual sensor elements because of the various structural conditionsof the vehicle seat.

[0013] According to the present invention, it is now checked by themanufacturer after installation, using a diagnostic tester, what sensorvalues the individual sensor elements have without a load on the seatingsurface, in order to derive correcting values from this, which offer acompensation for such mechanical stresses caused by the installation,and are then used as correcting values during operation.

[0014] In FIG. 1, that configuration is shown as a block diagram inwhich a diagnostic tester is connected to a control unit which isconnected to a seat mat. A diagnostic tester 1 is connected to a controlunit 2 for a seat mat, via a data input/output. At a data input ofcontrol unit 2, a seat mat 3, having various sensor elements that areshown as circles here, is connected. Via additional data inputs andoutputs, not shown here, control unit 2, is connected, for example, viaa bus to other vehicle components such as a restraint system, in orderto transmit the seat mat data, that is, the sensor values, to thesevehicle components in raw and/or evaluated form.

[0015] In the form of a block diagram, FIG. 3 shows the innerconstruction of diagnostic tester 1 and of control unit 2. Diagnostictester 1 has a data transmission interface 10, via which diagnostictester 1 is connected to control unit 2. Data transmission interface 10is connected to a processor 11 of diagnostic tester 1 via a datainput/output. Processor 11 is connected to a memory 12 via a second datainput/output. The setpoint values and the password are stocked up inmemory 12. Processor 11 is used for comparing setpoint values withsensor values and for evaluating the password interrogation.

[0016] Data transmission interface 10 is used for carrying out the datatransmission between diagnostic tester 1 and control unit 2. Controlunit 2 has a first data transmission interface 13, a memory 15 and aprocessor 14, which here is a microcontroller. Data transmissioninterface 13 is connected to data transmission interface 10 ofdiagnostic tester 1 via a first data input/output. Data transmissioninterface 13 is connected to processor 14 via a second datainput/output. Processor 14 is connected to memory 15 via a datainput/output. At a third data input/output, processor 14 is connected todata transmission interface 16. Data transmission interface 16 connectscontrol unit 2 to sensor mat 3 via its second data input/output. Memory15 is used for stocking up the password and the correction values forthe sensor values. Processor 14 carries out the correction of the sensorvalues before they are processed further. Data interfaces 13 and 16 areused for data transmission involving diagnostic tester 1 and sensor mat3.

[0017] In FIG. 2, the method according to the present invention isrepresented as a flow chart. In method step 4, diagnostic tester 1 isconnected to control unit 2, specifically by the connection via datatransmission interfaces 10 and 13. After initialization of the datatransmission connection between diagnostic tester 1 and control unit 2,control unit 2 interrogates diagnostic tester 1 for a password, andterminates the method if the password of the diagnostic tester is notcorrect.

[0018] However, if the password is correct, then, in method step 6, thereading out of the sensor values of sensor mat 3 by diagnostic tester 1is carried out. In method step 7, processor 11 now makes a comparison ofthe sensor values with setpoint values, which processor 11 loads frommemory 12. The difference between the setpoint values and the sensorvalues are then transmitted by diagnostic tester 1 to control unit 2 asthe correcting values. Processor 14 stores these correcting values inmemory 15 in method step 9. During the operation of sensor mat 3,processor 14 then corrects the sensor values read out from sensor mat 3,and the correcting values in memory 15. Thus the correcting values areused for calibrating the sensor values. The method is applied to anunloaded seating surface, so that only mechanical tensions conditionedon the installation of sensor mat 3 influences the sensor cells.

What is claimed is:
 1. A method for adjusting the sensor cells of a seatmat (3) to a mechanical stress caused by the installation of the seatmat (3) in a vehicle seat, wherein a diagnostic tester (1) is connectedto a control unit (2) for the seat mat (3); sensor values of the sensorcells are read out by the diagnostic tester (1) via the control unit(2); the sensor values are compared with setpoint values by thediagnostic tester (1); and as a function of the comparison, correctingvalues for the sensor values are transmitted to the control unit (2) forthe adjustment of the sensor cells.
 2. The method as recited in claim 1,wherein the correcting values are stored in a first memory (15) of thecontrol unit (2).
 3. The method as recited in claim 1 or 2, wherein apassword interrogation by the control unit (2) to the diagnostic tester(1) is carried out before the transmission of sensor values from thecontrol unit (2) to the diagnostic tester (1).
 4. A diagnostic testerfor carrying out the method as recited in one of claims 1 through 3,wherein the diagnostic tester (1) has a first data transmissioninterface (10) for connecting to the control unit (2), a second memory(12) for the setpoint values and the password, and a processor (11) forcarrying out the comparison between the setpoint values and the sensorvalues.
 5. A control unit for the seat mat (3) for carrying out themethod as recited in one of the claims 1 through 3, wherein the controlunit (2) has a second data transmission interface (13) for connecting tothe diagnostic teeter (1), a third data transmission interface (16) forconnecting to the seat mat (3), a processor (14) for evaluating thesensor values and a memory (15) for accommodating the correcting values.